Holographic diffusers for endoluminal-scale optical ultrasound imaging.

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Optics

Background:

• Freehand optical ultrasound (OpUS) uses fiber-optic sources and detectors for real-time imaging.
• Previous OpUS probes faced limitations in source design, probe size, and image quality due to waveguide integration.

Purpose of the Study:

• To introduce an improved method for generating eccentric fiber-optic OpUS sources using a holographic diffuser element (HDE).
• To overcome the size and performance limitations of existing freehand OpUS probes.

Main Methods:

• An anisotropic holographic diffuser element (HDE) was employed to shape fiber-delivered excitation light.
• The HDE was imprinted into a UV-curable adhesive for enhanced optical resilience and ease of alignment.
• This facilitated dense packing of optical fibers, creating a high-channel-count, small-diameter OpUS probe.

Main Results:

• The HDE enabled dense fiber packing, achieving a source pitch below the Nyquist limit and eliminating grating lobe artifacts.
• A 144-source freehand OpUS probe with endoluminal-compatible dimensions (18.5 mm diameter) was successfully fabricated.
• The probe demonstrated video-rate, real-time imaging with enhanced image quality and depth.

Conclusions:

• The HDE-based approach significantly improves freehand OpUS probe design and performance.
• This advancement allows for higher quality, real-time ultrasound imaging.
• It also enables the first successful endoluminal freehand OpUS imaging in a realistic phantom, paving the way for clinical applications.